Burning through 1/3 of oil over 5k miles

[patssle]

Well after a year of ownership and about to do my second oil change...I finally got a good count on oil consumption as I wasn't keeping tracking the first 5k miles.

I've burned through about 3 quarts of Mobile1 0w40 oil over the past 5000 miles. No drips or leaks - my garage floor and work spot are both clean. This 2000 S was a garage queen with 45k miles when I rescued her 1 year ago and had very little miles put on her over the last couple years of previous ownership. I run her hard when I can but let her warm up properly and without idling. Filled to and kept at halfway on the digital meter. My first 5k miles I used 15w50 oil and I don't believe it burned as much (but no accurate usage tracking was done) - so either it's getting worse or the thicker oil makes a difference. Will switch back to 15w50 for summer driving.

What do you guys think...burning oil isn't normal for Boxsters it seems. Am I going to have an engine failure at some point? Are the rings probably bad from sitting for so long and cracked? Or something else?